The invention relates to a single-channel communication bus system whereto a series of stations are connected, that is to say at least one master station and at least one slave station, each master station comprising arbitration means for transmitting a start signal, followed by a priority signal, and for detecting a negative or a positive arbitration result, in dependence of the start and/or priority signal of any other station, and also comprising transmission means for transmitting a message signal after a positive arbitration result. A system of this kind is known from Netherlands Patent Application No. 8002345 and the corresponding U.S Pat. No. 4,429,384. Single-channel buses may comprise a single conductor or a symmetrically driven twisted pair of conductors; the bus can alternatively be realized by means of optical means. The arbitration means are effective in that the bus realizes a wired logic function, for example a wired AND-function. This can be realized by means of an open collector connection of the stations and the like: each station supplying a logic 0 then masks any logic 1 delivered by any other station. The operation is the same in the case of an optical system.
The known system is well-defined at the bit level, but does not describe the actions to be undertaken when one of two communicating stations is incapable of correctly processing the information applied to it.